Light sensitized lead printing compounds and process of reproduction



Patented Jan; 28, 1947 PATENT 2,4lld,839

' LIGHT SENSITIZED mm ramrmo COM POUNDS AND PROCESS or REPRODUC TION Andi- Schoen, Eastomlaf, asslgnor to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware No Drawing.

Application January or, 1945, Serlal No. 575,557

15 Claims. (Cl. arte) The present invention relates to light sensitive printing papers and the like containing lead compounds and to the process of image development A thereof. It relates also to the super-sensitizationof such compounds to increase the speed or sensitivity thereof to light.

light sensitive compoundsot lead in photographic processes, and develop the latent image by a physical developer, but such processes have not attained any commercial importance, possibly due to the difficulties in development thereof and the long exposure time required for formation of the latent image.

It is an object of the present invention to provide a process for chemically developing light sensitive lead compositions.

Another object of the present invention is to super-sensitize, that is, increase the sensitivity to'light of, light sensitive lead compounds A further object is the provision of a photographic process employing a suitable base carrying a light sensitive lead compound.

According to one feature of the present invention the latent image on a base carrying a light sensitive lead compound which has been exposed to light undera pattern or the like to be reproduced, is developed by treatment with a strong reducing agent, resulting in a print or photograph in black and white. The invention may be carried out in practice by coating any suitable base with a light sensitive lead compound, and after drying,

the base is exposed to a suitable source of light under a suitable negative carrying the design to be reproduced, then the base is developed in a. solution having a strong reducing action, and is washed and dried. By the term strong reducing :agent I mean an agent with sufiicient reducing potential to bleach or discharge azo dyes, for example, Beta Naphthol Orange (C. I. 151).

In accordance with another featured the invention, the sensitivity to light of lead compounds supported on a suitable base is enhanced by treatment with a substance containing 3. mmcarbyl radical, especially an aminothlocarbyl radical, such as a thiocarbamido group. Examples of such substances are, sodium sulfoxylate' formaldehyde, sulfinoformamidine or allylthiourea. Compositions so treated after'exposure to light, are preferably developed with a strong reducing agent in solution as abovedescribed.

Preferably the light sensitive lead compounds which are water insoluble are precipitated on the support, such as a paper sheet, plate or the like,

although if desired, a gelatin solution or emulsion of the light sensitive lead compounds may be applied. The lead compounds may be treated with the supersensitizing material before, at the 5 same time or after being applied to the base, car I rier or support as desired. Preferably the base is Heretofore, it has been proposed to employ the first treated with a soluble lead compound and then is treated in the dark with a soluble base exchange compound to precipitate on the base the insoluble light sensitive compound. Thus, the

supersensitizing compound may be present in one of the base exchange solutions, 'or may be applied after precipitation of the insoluble light senal-= tive lead compound.

Light sensitive sheets, plates or the like this prepared preferably are employed in the print through process wherein light is transmitted from a suitable source through the negative to the sen sitized lead compound coated sheet for the re- 0 quired time to develop a latent image, which is then developed by solutions of strong reducing \agents. Such strong developer solutions maybe used todevelop sheets carrying light sensitive lead compounds with or without treatment with the supersensitizer herein described, and no fixa solution of a soluble ionized chloride, such as sodium chloride, or. cadmium chloride, or am monia, or potassium dichromate or the like. I believe the moisture stabilizers provide 9. protecting layer of an insoluble lead compound, but

do not wish to be limited to this theory in claiming my invention.

The lead image may be toned by any of the toners free from sulfides employed for silver images, for example, by treatment with'a solution 40 containing potassium ferricyanide, ferric ammonium citrate and acetic acid, which changes the image to blue and renders the image more stable. Preferably, such toners free from noble metals are employed.

As suitable light sensitive lead compounds of a base coated with lead asid and supersensltized with sodium sulfoxylate formaldehyde, by a sufliciently long exposure to light rich in ultra violet rays a black. print may be obtained directly that is, without development with a reducing by a base exchange reaction in aqueous solution, agent, although in general it is preferred to carry out the exposure for a shorter time and develop the latent image with a strong reducing agent. As examples of suitable strong reducing agents having a reducing potential suficient to bleach or discharge azo dyes, may be mentioned sodium hydrosulfite. sodium stannite, sulfinoformamicle (HSO CNHmNH), titanous chloride, titanous sulfate or the like.

- The invention will be described in further detail in connection with the following examples which are given to illustrate the invention.

Example I A sensitized paper is prepared by treating a paper base with a solution of 20 g. lead acetate in 100 cc. water, drying, then treating the paper in the dark with a solution of 20 g. potassium iodide in 100 cc. water, drying, and then treating the paper in the dark with a solution of g. sodium sulfoxylate formaldehyde in 100 cc. water and drying. Th sensitized paper is exposed under a negative in a printing frame for about one Example II A paper base coated with lead azide is prepared by first treating the paper with a solution of 20 g. lead acetate in 100 cc. water, drying then treating it in the dark with a solution of 15 g. sodium azide in 100 cc. water and drying. The light sensitive paper is exposed to a suitable source of light under a negative to form a latent image which is then developed as described in Example I. The developed positive is then treated for about two minutes in a solution of sodium chlo ride of about five to ten percent strength, and

then dried. There results a positive black a'nd white print.

Iclaim:

l. The process which comprises exposing to light under a pattern to be reproduced a lightsensitive layer on a suitable support comprising a light-sensitive lead compound and developing the thu formed latent image in a solution of a strong reducing agent selected from the group consisting of sodium hydrosulfite, sodium stannite, titanous chloride and titanous sulfate.

2. The process which comprises exposing to light under a pattern to be reproduced a lightsensitive layer on a suitable support comprising a light-sensitive lead compound and a supersensitizing agent selected from. the group consisting of sodium sulfoxylate formaldehyde, sulfiinoformarnidine, and allylthiourea, and developing the latent image thus formed in a solution of a strong reducing agent selected from the group consisting of sodium hydrosulfite, sodium stannlte, titanous chloride and titanous sulfate.

3. The process which comprises exposing to light under a pattern to be reproduced a lightsensitive layer on a suitable support comprising a light-sensitive lead compound and developing the thus formed latent image in a solution of an alkali metal hydrosulfite.

4. The process which comprises exposing to light under a pattern to be reproduced a lightsensitive layer on a suitable support comprising a light-sensitive lead compound, developing the thus formed latent image in a. solution of an alkali metal hydrosulflte and treating the developed image with a soluble inorganic chloride moisture stabilizer.

5. The process which comprises exposing to light under a pattern to be reproduced a, lightsensitive layer comprising lead iodide on a suitable support and developing the latent image thus formed in a solution of sodium hydrosulfite.

6. The process which comprises exposing to light under a pattern to be reproduced a lightsensitive layer on a suitable support comprising lead iodide and sodium sulfoxylate formaldehyde and developing the latent image thus formed in a solution of sodium hydrosulfite.

'7. The process which comprises exposing to light under a pattern to be reproduced a lightsensitive layer comprising lead bromide on a suitable support and developing the latent image thus produced in a solution of sodium hydrosulfite.

8. The process which comprise exposing to light under a pattern to be reproduced a lightsensitive layer on a suitable support comprising lead bromide and sodium sulfoxylate formaldehyde and developing the latent image thus formed in a solution of sodium hydrosulfite.

9. The process which comprises exposing to light under a pattern to be reproduced a lightsensitive layer comprising lead'azide on a suitable support and developing the latent image thus produced in a solution of sodium hydrosulfite.

10. The process which comprises exposing to light under a pattern to be reproduced a lightsensitive layer on a suitable support comprising lead azide and sodium sulfoxylate formaldehyde and developing the latent image thus produced in a solution of sodium hydrosulfite.

11. A light-sensitive article comprising a support carrying a light-sensitive lead compound and a supersensitizing agent selected from the group consistin of sodium sulfoxylate formaldehyde, sulfinoformamidine and allylthiourea.

12. A light sensitive article comprising a support carrying a light sensitive lead compound supersensitized with sodium sulfoxylate formaldehyde.

13. A light sensitive article comprising a support carrying lead iodide supersensitized with sodium sulfoxylate formaldehyde.

14. A light sensitive article comprising a support carrying lead bromide supersensitized with sodium sulfoxylate formaldehyde.

15. A light sensitive article comprising a support carrying lead azide supersensitized with sodium sulfoxylate formaldehyde.

ANDRE SCHOEN. 

